An electric switch is known for example from U.S. Pat. No. 4,139,748. In the case of this known switch, the drive shaft is part of a traveling mechanism of the electric switch for making the switch travel in relation to a withdrawable rack.
In this respect, the drive shaft has a flange provided with three slits. Depending on whether the switch is in the isolating position (main isolating contacts and auxiliary isolating contacts of the switch are open), test position (main isolating contacts are open, auxiliary isolating contacts are closed) or operating position (main isolating contacts and auxiliary isolating contacts are closed) in the withdrawable rack, a blocking pawl engages in one of the three slits under the force of a biasing spring and consequently prevents the drive shaft from being turned by use of the crank handle.
The blocking pawl and the flange must in this case produce a blocking action which corresponds to the high torque transmitted from the crank handle to the drive shaft. They therefore have to meet high requirements with respect to their dimensioning and strength. In order to make the switch travel, i.e. to actuate the drive shaft, the blocking pawl must be disengaged from the respective slit against the force of the biasing spring by way of an actuator which is coupled to the blocking pawl by means of a slot-pin connection. The actuator in this case passes through an opening on the front side of the switch.